The present invention relates to a variable-capacity intake system for an internal combustion engine, in particular a high-performance GT car engine.
As is known, it is possible to enhance the volumetric efficiency of an internal combustion engine using a system, which provides for varying intake conditions and optimizing engine filling by determining resonance conditions in the system at different engine speeds. Increasing the volumetric efficiency of the engine provides to a certain extent for increasing power output for a given engine speed, reducing fuel consumption by burning the fuel better, and hence reducing the amount of pollutant exhaust gas produced.
The state of the art is familiar with intake systems for internal combustion engines, especially those of high-performance, e.g. GT, cars, in which the air intake conduits comprise so-called "trumpet" elements designed to vary their length to diameter ratio and so vary the intake conditions of the engine. Such elements are substantially of two types: a first presents a telescopic end conduit portion defined by two coaxial elements sliding one inside the other and which, by varying their axial position in relation to each other, provide for varying the length to diameter ratio (the length increasing or decreasing, and the diameter remaining constant); and a second presents an inlet portion comprising a pair of semicylindrical lobes hinged to each other and laterally superimposed to define a continuous-section conduit portion variable in diameter according to the extent to which the two lobes are parted.
In the case of engines with no trumpet elements, use is made, for each cylinder, of two parallel intake conduits of appropriate length and diameter and end-connected by a manifold fitted inside with a throttle valve. By controlling the throttle valve, it is possible to use either one or both of the conduits, thus changing the "equivalent diameter" of the resulting intake conduit, and so achieve resonance conditions for a given number of different engine speeds.
The above systems present the drawback of being relatively bulky and expensive; and the first, featuring telescopic trumpet elements, is also relatively delicate in terms of mechanical control.